Field
Embodiments described herein relate to techniques for improving visibility in medical images.
Background
In many medical imaging modalities the dynamic range of acquired data exceeds the dynamic range of the device used for display, for example, Magnetic Resonance (MR) is 16 bit, Computed Tomography (CT) is 12 bit, and displays are 8 to 10 bits per channel. In most medical imaging applications, techniques known as Window & Leveling (or window width and window level) and color-mapping are used to control how an image is presented on the display.
The human visual system is very poor at determining the relative brightness of objects that are not adjacent. In the example shown in FIG. 1, the shade of gray of tiles A and B is exactly the same.
When a small window width is used to obtain good local contrast there will be areas of the image that are mapped outside of this range and will therefore be clamped to 100% black or 100% white, as shown in FIG. 2. This clamping hides information that is present in the original image data.
On the other hand, when a large window width is used it becomes more difficult to differentiate the boundaries between interesting structures, as shown in FIG. 3. This is because the boundaries are more likely to be mapped to similar gray levels. In these systems a particular data value is always mapped to a specific output color